Method of distilling tar



Oct. 10, 1933.

s. P. MILLER 1,930,130

METHOD OF DISTILLING TAR Filed June 24, 1927 2 Shets-Sheet l ATTORNEYSOct. 10, 1933. s. P. MILLER METHOD OF DISTILLING TAR 2 Sheets-Sheet 2'Filed June 24. 1927 INVENTOR 3 fgfiw ATTORNEYS Patented Oct. 10, 1933UNITED STATES PATENT QFFICE METHOD OF DISTILLING TAR Application June24, 1927. Serial No. 201,222

5 Claims.

This invention relates to improvements in the distillation of tars oroils, particularly to the utilization of the heat available in the gasesproduced in coal carbonization plants to distill coal gas condensatesand to the production of oils and tars. The invention will be describedespecially with reference to its application to coke ovens.

In the ordinary operation of by-product coke ovens, the gases producedby the coking operation pass from the individual ovens through uptakepipes and goose-necks to a collector main common to the ovens of thebattery. The gases commonly known as foul gases leave the ovens at hightemperature, e.g., 609 to 700 C., or higher, and carry a considerableproportion of vclatilized and entrained tars and oils as well as solidparticles of coke, coal and carbon and other impurities. Ordinarily, thegases are cooled as rapidly as possible by the application of sprays ofammonia liquor or ammonia liquor and tar in the goose-necks andcollector main, the heat in the gases being thereby dissipated and lost.The rapid cooling causes separation of tar containing heavier oils inthe collector main. Further cooling is effected in the crossover mainwhich connects the collector main to the condensing system, and anadditional quantity of tar carrying both heavier and lighter oils isrecovered in the cross-over main and in the condensers. The collectedtar is ordinarily shipped from the coke oven plant to a tar distillationplant for distillation and separation of the oils and production ofpitches of varying qualities. Handling losses, freight charges anddistillation costs, including fuel and capital and maintenance expensesfor the special equipment required for distillation add to the cost ofproduction of the tar distillation products.

It is the object of the present invention to provide method andapparatus for the production of marketable pitch or tar and salable oilsdirectly at a coal distillation plant by scrubbing the hot gases toremove impurities, separating salable oils from the resulting gases andvapors which have been more or less cleaned by the scrubbing operationand enriching gases from selected ovens by volatilizing residue from thescrubbers therein.

According to the usual practice, the condensates obtained in theoperation of coke ovens are collected as tar and contain considerableamounts of dust, coke braize, and free carbon. It is one of the purposesof this invention to treat the hot coke oven gases in such a manner asto allow the subsequent direct recovery of salable distillate oilfractions and salable pitches, thus avoiding the necessity fordistillation of tar as ordinarily carried out.

On cooling coke oven gases, according to the ordinary methods, a fog ormist of tar particles is produced. Due to the extremely small size ofthese particles, the tar persists in large quantities in the gases evenafter cooling to atmospheric temperatures. Hence, oily fractionsrecovered by step-wise cooling of the gases have been contaminated withtar and the fractions have not beensalable. It has been necessary todistill them for production of salable oils; the residue from thedistillation has been pitch. It

is one of the purposes of this invention to recover salable oils directfrom the gas stream.

According to the present invention, the coke oven gases are scrubbedwith tar or tar constituents preferably at high temperature, and by thisscrubbing both entrained tar and free carbon are removed from the gases.The scrubbing may be carried out in any one of a number of devicesadapted for the purpose. According to the preferred form'of the presentinvention, the scrubbing is eiiected by a spraying device, e. g., in ascrubber tower, located in the hottest part of the cross-over main nearthe exit from the collector main. At this point the gases are hot andscrubbing removes solid matter and entrained tar Without condensing anyconsiderable amount of the heavy oils. By controlling the temperature ofthe gases at this point and by controlling the temperature of the mediumsprayed into the scrubber, the quality of the tar or pitch recovered bythe scrubbing may be regulated. If the gases are very hot and a hotspray is used, a heavy pitch may be recovered and heavy constituents ofthe gases from which free carbon and entrained mist have been largelyremoved may be thrown forward into the coolers Where heavy constituents,as well as lighter constituents, will be recovered in an almost purestate, containing only a small percent, if any, free carbon.

The temperature of the gases may be con absorb a great quantity of thelatent and sensible heat of the gases and oil vapors, a lesser quantityof water or ammonia liquor may be sprayed into the collector mainsufficient to flush the main to prevent clogging, and at the same timeallow the gases leaving the collector main to maintain a hightemperature. Although by spraying the gases with less aqueous solutionthe temperature of the gases leaving the collector main may bemaintained at a higher temperature than the usual practice allows,because of the high latent heat of water and ammonia liquor, it isdesirable, for the purposes of this invention, to spray with tar or tarconstituents in the collector main instead of the usual aqueoussolution. By this procedure, the temperature of the gases is not loweredto the same extent as would result from spraying with the same quantityof an aqueous solution, and the vapors are enriched with desirabledistillates by volatilization of the spray. Agitation of thenonvolatilized residue in the collector main increases the distillationeiiected there. By decreasing the amount of oil or tar sprayed into thecollector main, or by preheating the spray, the temperature of the gasesentering the crossover main may be further increased. By maintaining ahigh temperature in the collector main, the quantity of heavy oilconstituents condensed there is kept at a minimum, and heavy oilconstituents are thrown over into the coolers in the vapor state. Afurther method of preventing condensation of heavy constituents in thecollector main is by dilution of the gases in the main with some inertgas.

, The heat of the gases leaving the coke ovens is sufiicient to distilla quantity of tar or oil many times that produced by the coke ovenitself. This invention, therefore, makes possible the production of alarge quantity of relatively clean distillates in addition to thoseproduced from the gases of the oven itself. Additional oils, tars, orpitches may be added to the system by spraying them into the hot gasesas they leave the coke ovens. This may be done in any suitableapparatus, such as the uptake still described in the application ofBrandon, Serial No. 154,746, filed December 14, 1926. By preheating thefluids sprayed into the uptake pipe, the capacity of one system forproducing pure distillates is increased.

By volatilizing tars or oils in the hot gases, the percent ofcondensable constituents in the gases may be increased by as much asfive or ten fold or more. Scrubbing removes solid and liquid impurities,viz., free carbon, tar fog, etc. By scrubbing enriched gases and thencooling to throw out condensable constituents, relatively clean oils canbe produced. Scrubbing removes impurities from the gases, and because ofthe previous enrichment of the gases in condensable constituents thepercentage of impurities remaining in the gases, when figured on thecon-- densable constituents is a great deal less than the percentage ofimpurities based on the condensable constituents in unenriched gases.

The scrubber not only serves to remove entrained solid and liquidparticles from the gases, but in certain cases, depending largely uponthe relative temperatures of the gases and the scrubbing medium andtheir respective compositions, light constituents of the scrubbingmedium may be volatilized to enrich the gases, or high boilingconstituents may be condensed out of the gases, or light constituents ofthe scrubbing medium may be volatilized and high boiling constituentsmay be condensed out of the gases simultaneously. When the gases are atrelatively low temperature, or the scrubbing medium is cold, only lowboiling constituents pass off with the gases. The composition of thegases and the non-volatilized constituents drawn off from the scrubberdepends upon the temperature of the gases and the scrubbing medium.Maintaining the gases entering the scrubber at a high temperature andpreheating the scrubbing medium tend to throw high boiling constituentsin both the gases and scrubbing medium forward into the condensers.

It is generally advantageous to use a scrubbing medium with atemperature above the dewpoint of the gases for the oil which it isdesired to throw forward into the coolers. If, for example, cool tar, i.e., tar lower in temperature than the gas stream is used as a scrubbingmedium, constituents which it is desired to recover in the condenserswill be thrown down with the tar at the scrubber, and a tar or pitchlighter than that obtained with a hot tar spray in hot gases will berecovered as residue from the scrubber.

Depending upon the quality of the oil, tar and pitch which it is desiredto recover, the nature of the recoverable constituents added to theprocess may be varied. Where several batteries of coke ovens areoperated in one plant, it is possible to equip the uptake pipes fromeach of the ovens of one battery with uptake stills, and to supply tothe uptake stills of this one battery 'tars, oils and pitches obtainedin the operation of the other batteries. The enriched gases may bescrubbed with any suitable tar, oil or pitch to produce a tar or pitchof desired properties in the scrubber, and the cleaned gases may becooled to recover salable products therefrom directly. By equipping onlya portion of the ovens of the battery in this way, it is possible toutilize the oils, tars or pitches, or desirable fractions of the oils,tars and pitches produced in the remainder of the battery in theoperation of the few ovens equipped with the uptake stills and scrubber.

By adding only the lighter fractions of tar and oils recovered from theoperation of other ovens to the ovens equipped with the scrubber,

a greater proportion of light oils will be recov ered, and, conversely,by adding a preponderance of heavier fractions a greater quantity oftars and pitches of high boiling point will be recovered. Instead ofcoke oven by-products, tar such as gas house tar, vertical retort tar,or Water gas tar, etc., or oils from various sources can be distilled byspraying in the uptake stills or collector main, or by using it as thescrubbing medium in the scrubber. When blended or composite pitches ordistillates are desired, several different kinds of tars, oils orpitches may be admixed in suitable proportions, and oil, tar or pitch ofthe desired composition may be obtained directly. For example,horizontal gas refrom the scrubbers may be pumped to the uptake stills,or the scrubber for the enriched gases.

This invention makes possible the production of nothing but relativelyclean oils, and the oils are recovered directly without the lossesentailed in the usual fractionation processes due to decomposition,handling losses, etc. Larger yields resuit with the possibility of areduced operating cost.

Tar as commonly produced and collected at coke oven plants contains moreor less water or ammonia liquor admixed therewith. Such tar can beemployed directly and dehydrated as well as distilled, or it can bepartially or completely dehydrated before subjecting it to distillation.

The tar or pitch may be preheated in any suitable manner to reduce it toa thinly fluid state and thus facilitate spraying into the gases andalso increase the capacity of the gases for distillation, therebythrowing over a larger quantity of higher boiling constituents into therecovery system beyond the scrubber.

The vapors in the gases leaving the scrubber may be condensed in onecondenser, or several fractions of difierent boiling points may beobtained by step-wise cooling. Removal of the tar fog entrained in thegases makes possible a sharper fractionation than is possible withoutsuch removal.

'Although the invention has been described in connection with a cokeoven system, and the drawings are confined to coke oven operation, it isintended and will be understood that features of this invention areapplicable to other operations in which gases containing entraina fog,dust or free carbon are produced, and it is intended and will beunderstood that this invention is not limited to the specific details ofthe apparatus as illustrated in the drawings or to a coke oven system.

In the drawings,

Fig. l is a plan view of a coke oven recovery plant illustrating oneadaptation of my invention; and

Fig. 2 is an elevation, partly in cross-section, through the shortcollector main connecting the ovens equipped with uptake stills of theplant shown in Fig. l.

Referring to the drawings, 5 is a coke oven battery with the usualuptake pipes 6 conveying hot coke oven gases to the usual collector main'7 from which the gases are withdrawn from the center-box 8 through thecross-over main 9. The gases are sprayed in the goosenecks and collectormain through sprays 10 with water or ammonia. liquor or tar or a mixtureof these.

The mixture of tar and ammonia liquor which is thrown down in thecollector main is drawn off through the center-box by the pipe 11 intothe decanter 12 from which ammonia liquor is run to the storage tank 13and tar is drawn off into the receiver 14.

The gases pass from the collector main to the cross-over main 9 and thenthrough the scrubber 15 in which they are sprayed through sprays 16 toremove solid and liquid impurities entrained in the gases and in certaincases to alter the composition of the gases if the ternperatures of thegases and scrubbing medium are so adjusted as to accomplish such aresult. The non-volatilized constituents of the scrubbing medium andgases thrown down in the scrubber are drawn off into the receiver 17,from which any ammonia liquor, if there be any, may be withdrawn intothe tank 18, and the tar or pitch drawn off into the receiver 19.

Tar or pitch collected in the receiver 19 may be used as a scrubbingmedium in which case it is pumped by the pump 20 to the sprays 13passing through the heat interchanger 21 in which its temperature may beeither raised or lowered. Tar or oil from another source, admittedthrough pipe 22, may be used as the scrubbing medium. The cleaned gasespass from the scrubberthrough the pipe 24 to the condensers 25 and 26,which may be wet condenser-s, and thence through the exhauster to thepipe 28 from which theymay be passed to other usual types of apparatus.Oils thrown. down in the condensers 25 and 26 withdrawn through the pipe29 to the decanter 30 from which ammonia liquor is withdrawn to the tank31 and clean oil to the receiver 32.

Uptake stills, such as those described in the copendin-g application ofBrandon above referred to, may be provided at the rear of sev eral ofthe ovens of the battery such as those indicated at in the drawings. Tarrecovered as a residue from the scrubber 15 may be supplied from thetank 19 to the uptake stills through the pipe 41 by means'of the pump42. The vapors and gases passing off from the uptake stills are passedover by the goose-necks 43 to the short collector main 44.

In each of the uptake stills, the gases pass up through the pipe 45 fromthe ovens and are diverted in their passage by the bafile' ili. Thegases are sprayedthrough one or more sprays l7 and by the intermittentcontact produced between the spraying medium and the hot gases, thelighter constituents of the spraying medl 1m are volatilized and pass01f with the gases and the heavier constituents collect in the lowerportion of the uptake still indicated at 4 3 and are drawn off throughthe pipe 49 to the re- 'ceiver 50.

The enriched gases from the uptake stills may be sprayed with tar orammonia liquor in the short collector main. Tar recovered as a residuefrom the usual collector main, collected in the tank 14, is a suitablespraying medium for the short collector main, and may be supplied to theshort collector main through the pipe 51 by the pump 52. Residue fromthe short collector main is withdrawn through the pipe 54 to thedecanter 55 "from which ammonia .iquor, (if there be any), is withdrawnto the tank 56 and tar or pitch to the receiver 57. Tar or pitchcollected in the receiver 57 may be recirculated through the collectormain through the pipe 53 by means or it may be sprayed into the uptakestills, in which case it will be withdrawn through the ipe 59 andsupplied by the pump 42 to the sprays 4'7. 1

Enriched gases from the short collector main are withdrawn through thecross-over main 60 and pass up through the scrubber 61 in which they arewashed by liquids supplied through the sprays 62. e The scrubbers l5 and61 may be of any suitable type as a tower filled with baiiles or gridsover which a suitable fluid is continuously flowing.

The non-'volatilized constituents collecting in the bottom of thescrubber 61 are withdrawn to the receiver 63, from which ammonia liquor,ii there be any present, is withdrawn to the tank 64 and tar or pitch iswithdrawn to tie tank 65. The tar or pitch withdrawn from the scrubbermay be recirculated through the sprays by means of the pump 66 throughthe pipe 6'. or

of the pump 52 the scrubber may be sprayed with tar, oil or pitch froman outside source through the pipe 68. The pipe leading to the sprays 62is equipped with a heat interchanger 69 for regulating the temperatureof the scrubbing medium.

Tar or pitch from the scrubber collected in the tank 65 may be used forspraying the short collector main, or it may be sprayed into the uptakestills, in which case it will be withdrawn from the tank 65 through thepipe 70 or 71, respectively. The short collector main may be sprayedwith ammonia liquor or tar or oil from an outside source through thepipe '72.

The enriched gases from the scrubber may be conducted to the condensers25 and 2'0, or they may be passed to fractional condensers 73, 74, '75and 75', and thence by the exhauster 27' to the pipe 28. The condensers73, 74, '75 and 75 are illustrative of any suitable condensing meanswhich may be provided. Instead of condensers as illustrated, condensersof any other suitable type may be provided. Clean oils are drawn fromthe condensers to the receivers 76, '77, 78 and 78. l

The system shown in the drawings provides for the operation of a batteryof coke ovens to produce only clean oils and marketable heavy tar orpitch. According to one preferred method of operation in which there areno other products than these, the scrubber 15 is supplied with residuefrom the tank 19 as a scrubbing medium, and the balance of the residuefrom the tank 19 not so used is sprayed into the uptake stills by meansof the pump 42 and pipe 41. The tar residue from the usual collectormain is withdrawn into the tank 1% and is supplied from there in part tothe short collector main, and the balance is sprayed into the uptakestills. The residue from the short collector main is supplied from the,tank 57 to the uptake stills. Residue withdrawn from the scrubber 61 isin part recirculated from the receiver 65 to the sprays 62, and thebalance is supplied to the uptake stills. Clean oil is re covered in thecontainers 32, '76, 77, '78 and 78. The only other condensate is the taror pitch drawn oiT from the uptake stills and collected in the container50.

Although the drawings and description provide for enrichment of thegases by volatizing residue from the scrubbers in uptake stills, it isintended and is to be understood that enrichment of the hot gases bythis residue in other means, such as by spraying into the collectormain, is included Within the scope of this invention.

Due to the spraying in the collector main followed by scrubbing in thescrubbers, the gases passing to the condensers are relatively clean, andthis is more especially true in the case of enriched gases. Theapparatus illustrated and operated according to the method outlinedyields relatively clean oils which are marketable in the condition inwhich they are recovered without being subjected to the distillationwhich the impure products recovered according to the usual practice mustbe subjected; The properties of the pitches or tars recovered in theprocess may be controlled within limits by the regulation oftemperatures and quantities of the spraying mediums used.

The invention is not limited to the illustrations given, but isapplicable to coal distillation in general and more particularly to cokeoven operation.

I claim:

1. The method of cleaning gases resulting from the carbonization of coalwhile the gases are still hot and producing oils from them whichcomprises dividing hot fresh coal carbonization gases from various coalcarbonizing units of the plant into two parts, cleaning one part of thegases at a high temperature to remove solid and liquid impuritiesentrained in the gases, distilling the matter thus removed from thegases in the other portion of the coal carbonization gases while theyare still hot and cleaning these gases at a high temperature to removeentrained solid and liquid particles, and cooling the cleaned gasesresulting from the treatment of the different parts of the gases toseparate clean oils.

2. The method of cleaning gases resulting from the coking of coal incoke ovens and producing clean oils which comprises collecting hot freshcoke oven gases from ovens of a battery in which coal is being coked intwo parts, scrubbing one part of the gases to remove entrained pitchparticles at a high temperature at which oils are present in the gasesin vapor form, bringing the pitch thus removed from the gases intodirect contact with the other part of the gases while still hot todistill the pitch and scrubbing this other portion of the gases whilestill hot to remove entrained pitch particles, and cooling the scrubbedgases resulting from the treatment of both parts of the gases so as tocondense and separate clean oils therefrom.

3. The method of cleaning gases resulting from the coking of coal incoke ovens and producing clean oils which comprises collecting hot freshcoke oven gases from a portion of the ovens of a battery in which coalis being coked one gas collecting system, partially cooling them thereinthereby separating tar from the gases, scrubbing the resulting gases ata high temperature to remove entrained pitch particles and collectinggases from the other ovens in another gas collecting system, anddistilling the tar and pitch by direct contact with these gases whilethey are still hot.

4. The method of cleaning gases resulting from the coking of coal incoke ovens and producing clean oils which comprises collecting hot freshcoke oven gases from a portion of the ovens of a battery in which coalis being distilled in one collector main, partially cooling them thereinthereby separating tar from the gases, scrubbing the resulting gaseswhile stillat a high tem perature to remove entrained pitch particleswhile retaining oils in vapor form, distilling the tar and pitch bydirect contact with gases from the other ovens collected in another gascollector main while still hot and scrubbing these gases at a hightemperature to remove entrained solid and liquid impurities, and coolingthe resulting two portions of scrubbed gases so as to condense andseparate clean oils.

5. The method of cleaning gases resulting from the coking of coal incoke ovens and producing clean oils which com rises scrubbing hot gasesresulting from the distillation of coal in a battery of coke ovens at ahigh temperature before they pass to condensers, and distilling at leasta portion of the tar or pitch separated from one portion of the gases bydirect contact withanother portion of the gases while still hot andbefore th y pass to the condensers to thereby enrich these gases incondensable constituents and produce pitch of high melting point.

STUART PARMELEE MILLER.

